I would not pay the price for either of these two guys, especially on a 3-5 year deal. Both will be seriously unready to pitch for a month after they sign, and I would bet arm soreness will arrive by rushing back.
Keuchel may well be a better choice , right now, than a Weber or Velazquez in the 5th starter role, but so should Eovaldi in a matter of days.
The best thing that can happen in June is for Mookie, JDM and Beni to play to their career averages. That would be an upgrade over the past few weeks. Add one consistent vet to the BP and that may be all that gets done sooner than July. Depending on June results, DD can better assess whether our marginal guys have any market value . Most don't.